This invention is generally relative to a dual-mode ultra wideband (UWB) and wireless local area network (WLAN) communications.
On Apr. 22, 2002, U.S. Federal Communications Commission (FCC) released the revision of Part 15 of the Commission's rules regarding UWB transmission systems to permit the marketing and operation of certain types of new products incorporating UWB technology. With appropriate technology, UWB devices can operate using spectrum occupied by existing radio service without causing interference, thereby permitting scare spectrum resources to be used more efficiently. The UWB technology offers significant benefits for Government, public safety, businesses and consumers under an unlicensed basis of operation spectrum.
The UWB devices can be classified into three types based on the operating restrictions: (1) imaging systems including ground penetrating radars and wall, through-wall, surveillance, and medical imaging device, (2) vehicular radar systems, and (3) communications and measurement systems. In general, FCC is adapting unwanted emission limits for the UWB devices that are significantly more stringent than those imposed on other Part 15 devices. In other words, FCC limits outdoor use of the UWB device devices to imaging systems, vehicular radar systems and handheld devices. Limiting the frequency bands, which is based on the −10 dB bandwidth of the UWB emission within certain UWB products, will be permitted to operate. For the communications and measurement systems, FCC provides a wide variety of the UWB devices, such as high-speed home and business networking devices as well as storage tank measurement devices under the Part 15 of the Commission's rules subject to certain frequency and power limitations. The UWB devices must operate in the frequency band from 3.1 GHz to 10.6 GHz. The UWB devices should also satisfy by the Part 15.209 limit, which sets emission limits for indoor and outdoor UWB systems, for the frequency band below 960 MHz, and the FCC's emission masks for the frequency band above 960 MHz.
For the indoor UWB communication operation, Table 1 lists the FCC indoor restrictions of the emission masks (dBm) along with the frequencies (GHz).
TABLE 1Frequency (MHz)EIRP (dBm) 0–960−41.3 960–1610−75.31610–1990−53.31990–3100−51.3 3100–10600−41.3Above 10600−51.3
The outdoor handheld UWB communication devices are intended to operate in a peer-to-peer mode without restriction on location. However, the outdoor handheld UWB communication devices must operate in the frequency band from 3.1 GHz to 10.6 GHz as well, with an extremely conservative out of band emission masks to address interference with other communication devices. The outdoor handheld UWB communication devices are permitted to emit at or below the Part 15.209 limit in the frequency band below 960 MHz. The emissions above 960 MHz for the outdoor handheld UWB communication devices must conform to the following emission masks as shown in Table 2:
TABLE 2Frequency (MHz)EIRP (dBm) 0–960−41.3 960–1610−75.31610–1900−63.31900–3100−61.3 3100–10600−41.3Above 10600−61.3
FCC proposed to define a UWB device as any device where the fractional bandwidth is greater than 0.25 based on the formula as follows:
                                          F            ⁢                                                  ⁢            B                    =                      2            ⁢                          (                                                                    f                    H                                    -                                      f                    L                                                                                        f                    H                                    +                                      f                    L                                                              )                                      ,                            (        1        )            where fH and fL are the upper and lower frequencies of the −10 dB emission points, respectively. The center frequency of the UWB transmission is defined as the average of the upper and lower −10 dB points. That is
                              F          C                =                                                            f                H                            -                              f                L                                      2                    .                                    (        2        )            In addition, a minimum bandwidth of 500 MHz must be used for indoor and outdoor UWB devices regardless of center frequency.
The indoor UWB communication devices must be designed to ensure that operation can only occur indoor according to the indoor emission masks in Table 1. The outdoor handheld UWB communication devices that may be employed for such activities as peer-to-peer operation must be designed according to the outdoor emission masks in Table 2. Both of the indoor and outdoor UWB communication devices can be used for wireless communications, particularly for short-range high-speed data transmissions suitable for broadband access to networks.
UWB communication transceiver for the indoor and outdoor operation can transmit and receive UWB signals by using one channel and/or up to 11 channels in parallel according to some embodiments of the present invention. Each channel of the UWB communication transceiver has a frequency bandwidth of 650 MHz that can transmit 40.625 Mega bits per second (Mbps). That is, a total of 11 channels are able to transmit 446.875 Mbps. The UWB communication transceiver also employs the orthogonal spread codes for all the channels. With 16 pseudorandom noise (PN) spread sequence codes for each bit, each channel achieves 650 Mega chips per second (Mcps). The UWB communication transceiver for the indoor and outdoor operation can transmit and receive the chip data rate up to 7.150 Giga chips per second (Gcps).
WLAN 802.11a is an IEEE standard for wireless LAN medium access control (MAC) and physical layer (PHY) specification and is also referred to as the high-speed physical layer in the 5 GHz band. The WLAN 802.11a standard specifies a PHY entity for an orthogonal frequency division multiplexing (OFDM) system. The radio frequency LAN communication system is initially aimed for the lower band of the 5.15–5.35 GHz and the upper band of the 5.725–5.825 GHz unlicensed national information structure (U-NII) bands, as regulated in the United States by the code of Federal Regulations under Title 47 and Section 15.407. The WLAN 802.11a communication system provides the data payload rate of 6, 9, 12, 18, 24, 36, 48 and 54 it/s Mbps. Also, the WLAN 802.111a communication system supports the transmitting and receiving at data rate of 6, 12, and 24 Mbps with mandatory. The WLAN 802.111a communication system uses 52 subcarriers with modulation of using binary or quadrature phase shift keying (BPSK/QPSK), 16-quadrature amplitude modulation (QAM), or 64-QAM. The forward error correction coding (FEC) of convolutional encoding is used with a coding rate of ½, ⅔, or ¾.
The UWB communication transceiver can achieve the transmission distance in a range of 3 meters to 10 meters since the UWB communication transceiver has to transmit the data with very-low power due to the restriction of FCC emission limitation for the indoor and outdoor operation. The UWB communication transceiver can transmit and receive a very-high data rate in the range from 40.625 to 446.875 Mbps according to some embodiments of the present invention. On the other hand, the WLAN 802.111a communication system can only transmit and receive the data rate in a range from 6 to 54 Mbps, but with a longer transmission distance up to 100 meters.
Since the UWB communication transceiver for the indoor and outdoor operation can transmit and receive the very-high data rate with the short-distance while the WLAN 802.111a communication system can transmit and receive the data up to a much longer distance than the UWB device, but has a lower transmission data rate for the device. Therefore, developing a dual-mode transceiver of the UWB communication system for the indoor and outdoor operation and the WLAN 802.11a communication system is very important since trade-offs of the transmission distance and data rate between the UWB and the WLAN 802.11a transceiver can be mutually utilized for benefits. This allows the UWB and WLAN 802.11a transceiver with co-existence in an environment.
Thus, there is a continuing need for a dual-mode UWB and WLAN 802.11a transceiver that operates using more than one standard and enables a user to use the same communication device in areas in which operate under different standards for the short-range wireless broadband communications.